| tag_t （tag_t类型） | udo_tag | Input（输入） | -- the tag for the UDO whose attention point is being defined |
| void * | display_context | Input（输入） | -- a pointer to a private structure used in display calls |
| tag_t （tag_t类型） | udo_tag | Input（输入） | -- the tag for the UDO who has an associated object being deleted |
| UF_UDOBJ_link_p_t | deleted_obj | Input（输入） | -- the link for the item that is deleted |
| tag_t （tag_t类型） | udo_tag | Input（输入） | -- the tag for the UDO being displayed |
| void * | display_context | Input（输入） | -- a pointer to a private structure used in display calls |
| tag_t （tag_t类型） | udo_tag | Input（输入） | -- the tag for the UDO which is being edited in the callback |
| tag_t （tag_t类型） | udo_tag | Input（输入） | -- the tag for the UDO being fit to the view |
| void * | display_context | Input（输入） | -- a pointer to a private structure used in fit calls |
| tag_t （tag_t类型） | udo_tag | Input（输入） | -- the tag for the UDO for which information is being requested |
| tag_t （tag_t类型） | udo_tag | Input（输入） | -- the tag for the UDO being fit to the view |
| logical * | is_occurrenceable | Output（输出） | -- TRUE if object can be occurrenced otherwise FALSE |
| tag_t （tag_t类型） | udo_tag | Input（输入） | -- the tag for the UDO being selected |
| void * | display_context | Input（输入） | -- a pointer to a private structure used in selection calls |
| tag_t （tag_t类型） | udo_tag | Input（输入） | -- the tag for the UDO being updated |
| UF_UDOBJ_link_p_t | update_cause | Input（输入） | -- the link for the item that caused the UDO to be updated |